System and method for storing and retrieving XML data encapsulated as an object in a database store

Abstract

A system and method are provided for modeling structured, semi-structured, and unstructured data all within a single instance of a user defined type (UDT) within a database store. In particular, the XML data model is extended to fields of a UDT. As a result, the properties of the XML data model—such as document order and document structure—can be preserved within instances of a UDT. Moreover, code representing object behavior (i.e., methods that can be invoked on an object in managed code) can be added to the UDT to operate on an XML field, as well as non-XML fields of the UDT. This enables a framework for adding business logic to XML data. The content model of the XML data can be optionally described using XML schema documents associated with the XML fields of the UDT.

1 . In a system in which an object that is an instance of a user defined type can be persisted in a database store, wherein a definition of the user defined type is provided as a class in managed code and comprises one or more fields and behaviors, each field having a respective data type, a method comprising: 
 defining a class in managed code that represents an XML data type for a field of a user defined type;    defining a field within the managed code class definition of a user defined type as an instance of the managed code class that represents the XML data type; and    persisting an instance of the user defined type within the database store, whereby a field of the persisted instance can contain XML data.    
   
   
       2 . The method recited in  claim 1 , wherein the managed code class that represents the XML data type comprises at least one constructor and at least one method that returns an object through which the XML data in the field of the persisted instance of the user defined type can be retrieved.  
   
   
       3 . The method recited in  claim 1 , further comprising adding a method to the managed code class definition of the user defined type to implement behavior on the field of the user defined type that is defined as an instance of the managed code class that represents the XML data type.  
   
   
       4 . The method recited in  claim 1 , further comprising the step of associating the field of an instance of the user defined type that contains XML data with an XML Schema that defines a content model for the XML data in the field.  
   
   
       5 . The method recited in  claim 4 , wherein said associating step comprises annotating the managed code class definition of the user defined type with an attribute that identifies the XML Schema on a server that hosts the database store.  
   
   
       6 . The method recited in  claim 1 , further comprising at least one of the steps of: 
 querying an instance of the user defined type persisted within the database store; and    modifying an instance of the user defined type persisted within the database store.    
   
   
       7 . A system comprising: 
 a runtime that provides managed code execution, the runtime comprising: 
 a class in managed code that represents an XML data type; and  
 a class in managed code that defines a user defined type for storage of objects of that type within a database store, the class definition for the user defined type comprising one or more fields, each field having a respective data type and at least one of said fields being defined as an instance of the managed code class that represents the XML data type; and  
   a database store for storing an instance of the user defined type, whereby a field of the persisted instance can contain XML data.    
   
   
       8 . The system recited in  claim 7 , wherein the managed code class that represents the XML data type comprises at least one constructor and at least one method that returns an object through which the XML data in the field of the persisted instance of the user defined type can be retrieved.  
   
   
       9 . The system recited in  claim 7 , wherein the managed code class that defines the user defined type further comprises a method that implements behavior on the field of the instance of the user defined type that contains XML data.  
   
   
       10 . The system recited in  claim 7 , wherein the managed code class that defines the user defined type further comprises an association between the field of an instance of the user defined type that contains XML data and an XML Schema that defines a content model for the XML data in the field.  
   
   
       11 . The system recited in  claim 10 , wherein the association comprises an attribute applied to the field within the managed code class that defines the user defined type, the attribute identifying the XML Schema on a server that hosts the database store.  
   
   
       12 . A computer readable medium having program code stored thereon for use in a system in which an object that is an instance of a user defined type can be persisted in a database store, said program code comprising: 
 a first class in managed code that represents an XML data type for a field of a user defined type;    a second class in managed code that defines a user defined type, the second class comprising one or more fields and behaviors, each field having a respective data type, at least one of the fields within the second class being defined as an instance of the first class,    said program code, when executed on a computer, enabling the computer to persist an instance of the user defined type within the database store, wherein said at least one field of the persisted instance contains XML data.    
   
   
       13 . The computer readable medium recited in  claim 1 , wherein the first class comprises at least one constructor and at least one method that returns an object through which the XML data in the field of the persisted instance of the user defined type can be retrieved.  
   
   
       14 . The computer readable medium recited in  claim 12 , wherein the second class further comprises a method that implements behavior on said at least one field of the user defined type that is defined as an instance of the first class.  
   
   
       15 . The computer readable medium recited in  claim 12 , wherein said at least one field of an instance of the user defined type that contains XML data is associated with an XML Schema that defines a content model for the XML data in the field.  
   
   
       16 . The computer readable medium recited in  claim 15 , wherein said at least one field is associated with said XML Schema by an annotation to the definition of said at least one field in the second class of an attribute that identifies the XML Schema on a server that hosts the database store.  
   
   
       17 . The computer readable medium recited in  claim 12 , wherein said program code further enables the computer to: 
 query an instance of the user defined type persisted within the database store; and    modify an instance of the user defined type persisted within the database store.